Interests

Hey everyone,
First off, let me just give some background information. My dream is to travel the world as a freelancer and I would like to start this venture by designing WordPress sites for small businesses. I was hoping someone with any experience in the industry could help me out with a decision.
Should I be using a page builder to design a clients website after choosing a fitting theme or would I best off learning all the useful languages involved in making wordpress sites? (I plan on using the genesis framework so I don't start from scratch each time.)
I love to learn, so I don't mind grinding it out to become more knowledgeable in these languages. However, I can't help but wonder if it would be more wise to use a page builder. I've done some research, but haven't really found much advice for a professional WordPress designer. Below, I'll lay out my hopes and concerns. I would be very grateful for any helpful input.
Hopes:
It might increase my efficiency. (Time is money, right?)
It might be easier to make customizations. It would shorten my learning curve and get me freelancing sooner.
Worries:
It might slow down the website.
It might negatively impact SEO and user experience. It would be unprofessional. I'm leaving something important out right now.
What do you think?

Hi guys,
A couple of days ago I encountered this slight hiccup:
Firstly..
I apologise if this doesn't belong in content management systems. Please advise me where to post this!
Secondly..
Has anybody else encountered this? When I click on 'visual' or 'text' nothing appears.
Thirdly..
I have a plugin called Page Builder, that had an update and since then I haven't been able to build pages like I used to!
I believe that this all happened at the same time.
Looking forward to any productive advice that you could possibly give me
(P.S. I have re-installed the latest version Wordpress to make sure.)